Phantom magneto telephone system



April 25, 1944.

c. s. RHoADs PHANTOM MAGNETO TELEPHOE SYSTEM Filed May 21, 194s 2sheets-sheet 1 SNL mvENToR BY Cllwaas ,ATTORNEY April 25, 1944. c. Vs.Rl-loADus 2,347,505

PHANTOM MAGNET@ TELEPHONE SYSTEM Filed .May 21, 1943 2 Sheets-Sheet 2lNVE-NTOR ATTORNEY Patented Apr. 25, 1944 UNITED STAT E S T NT FFECEPHANTOM MAGNETO TELEPHONE SYSTEM Applcation lJlay 21, 1943, Serial No.487,891

10 Claims.

This invention relates to telephone systems, and more particularly tophantom circuits for telephone systems. Still more particularly thisinvention relates to arrangements for providing a phantom circuit fromtwo telephone trunk circuits, the phantom circuit being equipped with amagneto. set for auxiliary signaling.

A community dial ofce, generally unattended, is often connected to amaster or operator oiiice, generally attended, by a number of trunkcircuits to enable subscribers in the area of the community dial ofce tocommunicate with the operator or subscribers in the areaV of the masteror operator omcey and, via that office, with operators or subscribers atmore remote points. The apparatus at the community dial oihce is usuallyarranged so that a subscriber may automatically select one ci the trunkcircuits by properly operating his dial set, It may happen, however.,that the selectors or switches that control the selection and seizurevof one of the trunks are busy or that all of the trunks are busy, inwhich case the operation of the dial set to establish a connection tothe operator at the master oliice or to any of they subscribers reachedvia that oiiice will be of no avail. Such a situation may be quiteserious, especially during periods of emergency.

Accordingly it is an object of this invention to provide a phantomcircuit by connection oi apparatus to two telephone trunk circuits toenable fr'.

a subscriber to signal either an operator at the master ofce or asubscriber in the area of "le master ofce when all selectors or switchesor trunks are busy. The phantom circuit of this invention involvesadditional equipment includp ing a magneto telephone set arranged sothat the operation of the magneto generator ofthe set will not interferewith signaling over the trunk circuits or cause false operation of thetrunk circuits.

This invention will be better understood from the more detaileddescription hereinafter 'following when read in connection with theaccompa nying drawings, in which Figure l illustrates a master ciice anda community dial cfce interconnected by trunk circuits and providedwith. a magneto telephone set inserted in a phantom circuit for use withthe trunk circuits side circuits, and Fig. 2 shows schematicallyswitciiing contacts controlled by the magneto generator of the magnetotelephone set and arranged to prevent interference with and falseoperation of the equipment of the trunk circuits. A

Referring to Fig. 1 of the drawings, two trunk circuits TK1 and TKz of agroup of similar trunk circuits are shown interconnecting a communitydial olce CDO', usually unattended, and a master oiiice MO at which oneor more operators may be in attendance. Each of these trunk circuits TKiand IKz may be employed for two-way signaling in a well known mannerbetween the two offices and between subscribers connected to the twooices. A magneto telephone set MS may also be connected tothe communitydial cnice CDO and this set may be located in the areav or" thecommunity dial oliice in the saine manner that the subscribers telephonesetsV S81 and S82, for example, are so` located. The magneto set MS isconnected tov the. trunk TK1 over parallel paths which includecondensers C1 and C2 extend-ing tothe upper and lower portions of theprimary windings of the transformer or repeating coil RC1. The magnetoset MS is likewise connected to the trunk TX2 by two parallel pathsincluding condensers C3 and C4 which extend to theY upper and lowerportions of the primary windings `of the` repeating coil or transformerRC2. The upper and lower windings of the battery and ground relay BGiassociated with trunk TK1 are connected to ground and battery B1,respectively, the paths to ground and battery including contacts ll andl, respectively, of the switching device K. Similarly the upper andlower `windings of the battery and groundrelay BGz associated with trunkTrie are connected to battery B2 and ground through the contacts I3 andit of the switching device K. When the switching device l is operated,the contacts ll, I2, I3 and it will .be opened, in which case the 'upperand lower windings of relay B Gl will be connected to ground and batteryBi through the 'rectifying elements RKl and EKL respectively,

and the upper and lower windings of relay BG2 will be similarlyconnected to battery E2 and ground throughthe rectiiying elements Rlsand RKL, respectively, The switching device K may be hand-operated or itmay, `if desired, be controlled by the operation of the magnetogenerator MG of the magneto set MS, as will be described moreparticularly with respect to Fig. 2. However, whenever the device 'K isoperated it controls. the addition of the rectiers R311 to RKi to therelays BGl and BGZ of the two trunk circuits TKl and 1K2. As will beexplained hereinafter, these rectiiiers rectify the current of themagneto generator MG, enabling the rectiied current to flow through thewindings of the relays EGi and BGrz unidirectionally and thereby preventthe release or chatter of these relays. The rectiiiers therefore preventfalse operation of the switching apparatus controlled by these relays.

At the master oice MO the upper and lower primary windings of therepeating coil or transformer RC3 are connected by the parallelcondensers C5 and Cs to one side of a jack Jo which may terminate thephantom circuit and the upper and lower primary windings of therepeating coil of transformer RC4 are similarly connected by condensersC7 and Ca, respectively, to the other side of the jack Jn. Thesecondensers are inserted in the circuit; so that the alternating currentproduced by the magneto generator MG of the magneto Set MS may alonecause the ringdown relay Ro to be operated. The relay R0 will beemployed to light a lamp Lo to signal the operator at the master oce forauxiliary or emergency purposes. The operation of the phantom circuit ofthis invention will be described somewhat more fully hereinafter.

The trunk circuits TK1 and TKz and the apparatus associated with thesetrunk circuits are of the usual type and they will be described onlybriey. Whenever the subscriber having the telephone set SS1 connected tothe community dial ofllce CDO desires to communicate with the operatorat the master oice MO, he will operate his dial set in the usual way.This will cause the selector or switching apparatus SW1 to nd an idletrunk such as TK1 and seize the trunk to complete a path to the masteroice. When the trunk TK1 is seized, current will flow from the batteryBa through the lower winding of relay BS1, the lower secondary windingof repeating coil RC1, through the apparatus SW1 to the telephone setSS1, and back over the upper conductor extending to the telephone setSS1, through the apparatus SW1 and then through the upper secondarywinding of the repeating coil RC1, the upper winding of relay BS1 andground. As relay BS1 operates it establishes an obvious circuit for theoperation of the relay BR1. When relay BB1 operates, its two armaturesreverse the connections to the conductors of trunk TK1, whereuponcurrent will flow from battery B1 over a .circuit including contacts I2of the switching device K, the lower winding of relay BG1, the lowerprimary winding of the repeating coil RC1, the lower armature and makecontact of relay BB1, the upper conductor of trunk TK1, the'upperprimary winding of repeating coil RC3, the windings of relay P1, thelower primary winding of repeating coil RC3, the contacts I1 of the dialjack DJ1, the lower conductor of trunk TK1, the upper armature and makecontact of relay BR1, the upper primary winding of repeating coil RC1,the upper winding of relay BG1, contacts H of the switching device K andground. The flow of this current through the windings of the polarizedrelay P1 is now in such a direction as to cause the relay P1 to becomeoperated. As relay P1 becomes operated it completes a circuit toilluminate lamp L1, the circuit including the armature and make contactof relay P1, the lamp L1, the armature and back contact of relay R1,battery B4 and ground. The illumination of the lamp L1 will attract theoperators attention and she will therefore insert her plug PL into thejack J1 which is associated with the lamp L1 and trunk TK1 to answer thecall.

Upon the insertion of plug PL into jack J1 a circuit will be establishedto operate relay R1, this circuit including the upper contact I9 0f jackJ1, the winding of relay R1 and ground. When relay R1 operates it opensthe circuit of lamp L1, thereby extinguishing the lamp L1. The operatorsset will then be connected to the telephone set SS1, over trunk TK1 toallow the operator and the subscriber to speak to each other. Asubscribers set such as SS1 may likewise be connected to the operator atthe master office through the equipment at the community dial oice CDOand over trunk 'IKz in the manner already described in respect totelephone subscribers set SS1.

The dial jacks DJ1 and DJz are shown connected to the trunks TK1 andTKz, respectively. The operator may connect her dial set to either ofthese jacks for connecting the trunk TK1, for example, to any one of thevarious subscribers sets such as SS1, SSz, etc. When the dial set isconnected to the jack DJ1, the dial pulses will be transmitted overthetrunk TK1 to operate the relay BG1 in accordance with the pulsesproduced by the dial, whereupon the armature of the relay BG1 will closeits contact a number of times to control switching apparatus forselecting any desired one of the various telephone circuits such as SS1,SSz, etc. The switching apparatus has not been shown in detail as it isnot required for an understanding of the invention.

The magneto set MS may be located on the same premises as either thesub-set SS1 or the sub-set SSz or at a different location. Whenever thesubscribers set SS1, for example, receives a busy signal after dialingthe operator or any of the subscribers in the areas of the two oices,the magneto generator MG may then be operated by hand for establishing aphantom circuit to the operator at the master office to attract herattention. Such a busy condition is not infrequent for it may ariseWhenever the selectors or switches such as SW1 and SW2 are busy or whenthe trunks TK1 and TKz are busy. The hand generator MG will transmit analternating current over the :phantom circuit proy vided by the trunkcircuits TK1 and TKz to operate the relay Ro at the master oilice, asalready stated. The interconnectedcircuit will include one path over theparallel condensers C1 and C2 and through the upper and lower primarywindings of the repeating coil RC1, the two conductors of the trunk TK1,the two primary windings of repeating coil RC3, the .parallel condensersC5 and Cs associated with the trunk TK1, the thermistor TH, the windingof relay Ro, the contact 28 of jack Jo, and then back over parallelcircuits including condensers C7 and Cs associated with trunk TX2, theupper and lower primary windings of repeating coil RC4, the twoconductors of trunk TKz, the two primary windings of the repeating coilRC2, the parallel condensers C3 and C4 to the generator MG. Thisalternating current will cause relay Ro to operate as already stated andcomplete an obvious circuit to illuminate lamp Lo. The operatorsattention will be attracted by lamp L0 and upon the insertion of herplug PL into jack Jo to answer the call, the lamp L0 will beextinguished.

When plugPL is inserted into jack Jo the operators telephone set will beconnected to the magneto set MS to enable the operator and thesubscriber controlling the magneto generator MG to talk with each other.The talking path at the master office will include the condensers C5 andCs which are connected to trunk TK1, and the condensers C1 and Cs whichare con- TK1 and TKz.

This undesirable condition, however, may be 'y nected to the trunk TKz.The talking path at the community dial -omce -CDO will include thecondensers C1 and C2, which are connected to trunk TK1, and condensersC3 and C4 which are connected to trunk TKz. The telephone transmitterand receiver of the magneto set MS will be connected to this phantomcircuit when the telephone receiver is removed from its switchhook SH.

It is noted that the upper terminal lof the magneto generator MG isconnected through parallel paths including condensers C1 and C2 and theupper and lower windings of relay BG1 to ground and battery B1,respectively, and that the lower terminal of magneto generator MG isconnected to the upper and lower windings of relay BG2 and battery B2and ground, respectively. The alternating current of magneto generatorMG may therefore traverse the windings of -both relays BG1 and BG1, andcause their false operation. These relays will alternately open andclose their respective make contacts in response to the generatedcurrent. As the make contacts of these relays are closed, the existingconnections (not shown) established through the armatures of theserelays to trunks TK1 and TK2 will be opened and hence the trunks TK1vand TKz may be released. Hence existing communication over trunks TK1and TKz will be terminated. In other words, the operation of the magnetogenerator MG may cause the relays BR1 and BRz to chatter and therebyinterfere with talking or signaling over the two trunks Such a conditionis undesirable.

overcome by simply operating switching device K.

When the switching device K is operated, it will insert rectifyingelements into the circuits ci the windings of relays BG1 and BGz. Withthe device K operated, contacts Il and I2 will be opened and rectifiersRK1 and RKZ will be connected between the upper and lower windings ofrelay BG1 and ground and battery B1,

respectively. Similarly contacts I3 and IA. will".

be opened, interposing rectiiiers RKg and RK; in the circuits betweenthe upper and lower windings of relay BGz and battery B2 and ground, re-

spectively. Thus, by so operating device K, cur-y rent will now nowunidirectionally through the' "i" upper windings of relays BG1 and BGzover a circuit which includes rectiiier RKi, the upper wind.- ing ofrelay BG1, condenser C1, the generator MG, condenser C3, the upperwinding of relay BGz, rectifier RKa, battery B2 and ground, Current willalso ow unidirectionally through the lower winding of relays BG1 and BGzover a circuit which includes battery B1, rectifier RKz, the lowerwinding of relay BG1, condenser C2, generator MG, condenser C4, thelower winding of relay BGz, rectier RK4 and ground, The unidirectionalcurrents now traversing both windings of relays BG1 and BGz will besuperimposed upon the direct currents previously supplied to thesewindings by batteries B1 and B2. Thus an inf. creased current willtraverse the windings lof relays BG1 and BGz and these relays will beheld operated while the hand generator MG is operated. These relaysremaining operated they will hold the Ytrunks TK1 and TK2 connected tothe subscribers sets such as SS1 and SSz and not interfere withcommunication over the two trunk circuits.

The condensers C1 and C2 provide a low irnpedance path between generatorMG and trunk TK1 for the alternating current generated .and condensersCs and C6 provide a low impedance path between trunk TK1 and relay R0Vso that only the generated current may actuate relay Ro. The returnpath for the generated current includes condensers Cv and Cs, trunk TK2and condensers C3 and C4. The rectifying elements RK1 to RK4 prevent theow of alternating current through the windings of the relay apparatuscommon to trunk TK1 or trunk TKz except in rectified form. Thusalternating current will be transmitted over the trunks acting astransmission paths extending between the two oflices, but the trunkcontrol apparatus will receive only direct current.

The rect'iers RK1 to R-K4 interposed in the circuits between the handgenerator MG and the windings of relays BG1 and BGz provide in effect afull wave rectifying circuit, Both halves of each cycle of alternatingcurrent produced by the generator MG will be rectified and the rectified current will be added to the battery currents previously flowingthrough these relay windings, Thus the rectied currents and the batterycurrents will be caused rto aid each other,

increase the holding action of relays BG1 and BGz and prevent theirchattering This is an important feature of this invention.

Fig. 2 shows schematically an arrangement for inserting the rectifiersRK1 to RKi of Fig. l into their respective circuits upon the operationof the hand generator MG. The crank of the hand generator MG whenrotated controls a cam 2S, which in turn may move the insulating bar 33to the left so asto open all of the contacts 3|, 32, 33 and 34simultaneously. Contacts 3l and 32 bridge the rectiers RK1 and RK2,respectively, and contacts 33 and 34 bridge rectiers RKS and RK4,respectively. When the arm 3l) is caused to move to the left in responseto the rotation of the crank of the generator MG, the contacts 3l to 34will be opened, thereby inserting the rectiiers RK1 to RK4 in theirrespective paths, as already described hereinabove with respect to Fig,l. At the same time contact 35 will be closed to establish a pathbetween the hand generator MG and the condensers C1 and C2. The contact35, therefore, interposes the hand generator MG in series between theparallel condensers C1 and Cz andthe parallel condensers C3 and C4.These condensers `are connected to the trunk circuits as shown in Fig'l.The switching arrangement of Fig. 2 is automatic in operation and opensthe bridge circuit to the rectiers just as soon as the crank ofgenerator MG is properly rotated. Although the arrangement of Fig. 2illustrates how the magneto generator MG may simultaneously close aplurality of contacts such as 3l to 35, it will be understood that thecam device 29 may close but one contact which in turn may control theoperation of a relay (not shown), the relay controlling the contacts 3lto 35 which shunt the rectiers RK1 to RK4. The relay obviously may belocated either at the station of the magneto telephone set MS or at thecommunity dial oice CDO, The contacts l2-l4 associated with the relaymay be adjacent to the relay or remote therefrom, as desired.

Although it has been stated that the magneto set may be operatedwhenever a busy condition develops on the trunk circuits between the twocilices, the magneto set may also be used even when the trunk apparatusis idle. The magneto phantom circuit provides an additional path betweenthe two oices for special use both for signaling and talking duringemergencies. The cost of the equipment required to set up the phantomcircuit is quite small. The additional equipment is simple and may beappended to the trunk apparatus whenever` desired. The magneto phantomcircuit will be operable whether or not the trunk circuits aretransposed with respect to each other.

Although this invention has been disclosed in certain specicarrangements which are deemed desirable, it will be obvious that thegeneral principles herein set forth may be embodied in many otherorganizations, widely diierent from those illustrated, without departingfrom the spirit of the invention as defined in the appended claims.

What is claimed is:

l. In a telephone system, the combination of a manual omce and acommunity dial -orcecon- -nected to each other by a pair of trunks, two

relays each connected to one of said trunks for controlling theconnection of the trunk to subscribers circuits, a magneto telephone setincluding a magneto generator connected to said trunks as a phantomcircuit, and means for preventing the magneto generator from falselyoperating the said relays.

2. In a telephone system, the combination of two trunks, two repeatingcoils one terminating each trunk, two relays each connected to themidpoint of one of the repeating coils, a magneto telephone setincluding a magneto generator connected between the midpoints of saidrepeating coils so that said trunks may provide a phantom circuit forsaid magneto set, a plurality of rectifying elements, and meansresponsive to the operation of the magneto generator for inserting saidrectifying elements in series with the windings of said relays so thatonly undirectional current may flow through the windings of said relays.

3. In a telephone system, the combination of a telephone line, a relayconnected to said line, a magneto generator, means for connecting saidmagneto generator to said line to energize the winding of said relay, arectifying element, and means responsive to the operation of saidmagneto generator to connect said reotifying element in series with thewinding of said relay so that only unidirectional current may ilowthrough said relay windings.

4. In a telephone system, the combination of a relay having twowindings, two rectifying elements, a telephone line connected to thewindings of said relays, a magneto generator, and means responsive tothe operation of said generator for connecting said rectifying elementsto the windings of said relay so that only unidirectional current mayflow therethrough.

5. In a telephone system, the combination of two trunks, two repeatingcoils each terminating one of said trunks, two relays one associatedwith each trunk and connected to the midpoint of the repeating coil ofthe associated trunk, a magneto telephone set including a magnetogenerator connected between the midpoints of the repeating coils of bothtrunks so that said trunks may form the side circuits of a phantomcircuit, a plurality of rectifying elements, and means responsive to theoperation of said magneto generator for inserting said rectifyingelements in circuit with said relay windings so that only unidirectionalcurrents may traverse the windings of said relays.

6. In a telephone system, the combination of two trunks, two repeatingcoils each terminating one of vsaid trunks, switching apparatus for saidtrunks, said switching apparatus including a relay for each trunkconnected to the midpoint of the repeating coil associated with saidtrunk, a magneto telephone set including a magneto generator connectedbetween the midpoints of the repeating coils associated with both trunksso that said trunks may provide a phantomcircuit for said magneto set,means responsive to the operation of the generator of said magneto setfor transmitting only rectified current through the windings of saidrelays, and apparatus controlled by the current produced by said magnetogenerator.

'7. In a telephone system, the combination of a pair of trunksinterconnecting two oiiices, a magneto telephone set including a magnetogenerator connected between both trunks at one of the ofces so as toprovide a phantom circuit,

vsignal responsive means connected between both trunks at the other ofthe ofces to complete the phantom circuit, switching apparatus connectedto each trunk, and means to prevent the operation of said switchingapparatus by said magneto set.

8. In a telephone system, the combination of a pair of trunksinterconnecting two offices, a telephone set including a ringinggenerator connected between both trunks at one of the oilces, signalingapparatus connected between both trunks at the other of the oices, saidtelephone set and said signaling apparatus providing with said trunks aphantom circuit,` switching apparatus connected to each trunk, and meansto prevent the ringing generator of the telephone set 'from falselyoperating said switching apparatus.-

9. In a telephone system, the combination of a pair of trunksinterconnecting two oiices, a telephone set including a ringinggenerator connected between both trunks at one cf the oiices, signalingapparatus connected between both trunks at the other of the oflices,said telephone set and said signaling apparatus providing with saidtrunks a phantom circuit, switching apparatus connected to each trunk,and means responsive to the operation of the ringing generator of saidtelephone set to prevent the release of the switching apparatus by thecurrent of said ringing generator when said switching apparatus isoperated.

10. In a telephone system, the combination of two telephone oflicesconnected to each other by a pair of trunks, a plurality of subscriberscircuits, two relays each connected to one of said trunks forcontrolling the connection of l the associated trunk to one of thesubscriber circuits, a magneto telephone set including a magnetogenerator which may be connected to said trunks as a phantom circuitwhen said trunks are busy, and means to prevent saidmagneto generatorfrom falsely operating said relays.

CHARLES STANLEY RHOADS.

